1. Field of the Invention
The present invention relates to a nonvolatile semiconductor memory device, and to a method of manufacturing the device.
2. Description of the Related Art
A nonvolatile semiconductor memory device, for example, a NAND flash memory is loaded in various electronic apparatuses. In the NAND flash memory, the shrinking of a memory cell transistor is advanced to increase a storage capacity.
For example, the microscopic processing technique (sidewall processing technique) (e.g., see Jpn. Pat. appln. KOKAI Publication No. 2007-335763) has been proposed in order to perform the shrinking of the memory cell transistor. According to the technique, an underlying layer is processed using a sidewall as a mask.
With the shrinking of the memory cell transistor, the area of a peripheral circuit area is reduced. However, it is difficult to perform the shrinking of a field-effect transistor formed on the peripheral circuit area.